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Tag Archives: district heating

Green heat in the UK

by Dave Elliott

‘Heat is very difficult to decarbonise and no consensus is yet reached on the mix needed for the long term and you will have seen that from the various different reports on the subject.’  So said the then UK Minister of State for Energy, Baroness Neville-Rolfe, at the Heat Summit last December, with the next phase of the Renewable Heat Incentive (RHI) central to the agenda. There certainly are some competing options, including community-wide heat networks, green gas supply networks, biomass and solar home heating and domestic heat pumps powered by electricity.

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What sort of green grid system?

By Dave Elliott

It’s clear that we will need energy transmission grids and networks to help balance variable renewables and link up locations where there is excess to areas where there are temporary lulls, but what sort of energy is best for transmission? And for storage? Both are important and can interact: in some cases storage may be better as a local option than long distance transmission, while in other cases, long distance transmission may allow access to areas where storage (e.g. pumped hydro reservoirs) is easier.  However, electricity isn’t necessarily always the best option for either: for example, gas can be transmitted long distances with low losses and, once installed, gas pipelines are less invasive than power grid tower links. Gas can also be stored in bulk in underground caverns and the gas grid itself is a store. So as we move to a new energy system, we need to think about all the possible energy vectors – and that also includes heat.

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Cities and renewable energy

By Dave Elliott 

Urban areas account for around 75% of the world’s energy use and there are ambitious plans to reduce their reliance on fossil fuels. Around the world, cities are beginning to think in terms of meeting their energy needs from renewable sources, so as to limit air pollution and climate change problems.  The case for this transition is strong, not least given the likely rise in air-conditioning demand as climate change impacts more,  and there have been many interesting initiatives launched around the world, often led by city governments.  (more…)

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Green heat infrastructure

By Dave Elliott

Imperial College has looked at Heat System Decarbonisation (PDF) in the UK in a new report. Provocatively it says solar and biomass heat can only play limited roles for direct space heating, and focuses mainly on three other low carbon system options: a shift to using hydrogen in the gas grid, the use of decarbonized electricity to run heat pumps, and the creation of local heat networks.

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ETI on energy saving in buildings

By Dave Elliott

The UK Energy Technologies Institute’s report by Jeff Douglas on Decarbonising Heat for UK Homes notes that ~20% of CO2 emissions are from domestic heating, but says insulation/upgrades won’t cut that enough: ‘the scope for cost effectively reducing the energy demand of existing buildings to the great extent required to meet emissions targets is limited as comprehensive insulation and improvement measures are expensive and intrusive. A several hundred billion pound investment in demand reduction for the entire building stock might deliver less than half of the emissions abatement needed. The most cost effective solutions therefore involve the decarbonisation of the energy supply combined with efficiency improvements that are selectively rather than universally applied, as part of a composite package’.

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Prosumer integration

By Dave Elliott

The German Environment Agency (UBA) has produced a comprehensive review of options for removing almost all (95%) greenhouse gas emission by 2050, based on the existing 80% renewables programme for electricity supply, but also looking at all the other sectors – including heating and transport. As I said in my coverage in an earlier post, that is pretty challenging. But it says it can be done. www.umweltbundesamt.de/publikationen/germany-2050-a-greenhouse-gas-neutral-country

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Devolving power

By Dave Elliott

‘Distributing Power: A transition to a civic energy future’, a report on research by the EPSRC-funded Realising Transition Pathways Research Consortium of 9 UK universities, argues that up to 50% of electricity demand in the UK could be met by distributed and low carbon sources by 2050. The report assesses the technological feasibility of a move from the current traditional business models of the ‘Big Six’ energy providers to a model where greater ownership is met by devolved governments, municipalities, co-ops and communities. And it looks in details at what types of governance, ownership and control a distributed future would need. (more…)

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Energy storage – new views, Part 2

By Dave Elliott

In addition to its large-scale grid balancing role, which I looked at in my last post, energy storage may also play a role at the consumer level, with batteries allowing solar PV-using ‘prosumers’ to provide their own backup. Some see this as a possible new type of distributed storage capacity and also, more radically, as further challenging the market power of the big utilities (much of the 75GW of wind and PV in Germany is now owned by local consumers and energy co-ops), even to the point when grid systems are redundant. This may be overstated, but some more movement in that direction may be occurring in Germany and the US as batteries get cheaper.   (more…)

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Green Heat 2

By Dave Elliott

The governments new Heat Strategy review took on board many of the arguments for district heating, and even the use of solar, that previously had been rather marginalised. It identified pathways for the transition of the UK’s heat supply to low- and zero-carbon energy sources in the domestic and industrial sectors.

The Combined Heat and Power Association (CHPA) was delighted. It said that ‘the Strategy points the way to a major expansion of new district heating networks in towns and cities, driving a multi-billion pound investment programme in green infrastructure and creating an additional 40,000 jobs in construction and engineering’.

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Green Heat 1

I have often been less than impressed by reports from the Royal Academy of Engineering (RAE) , which usually seems to take a conservative line on energy issues, but their new report on heating for buildings seems overall very well done, although with lapses. It makes the sensible point that we need to deal with the building envelop first, but also notes that most of the houses that will be lived in by 2050 have already been built, so we must look to remedial measures. It also notes that ‘Manchester isn’t Leipzig’, and looks at patterns of heating need and perceptions of comfort. It assumes we are talking about well insulated buildings, and familiar levels of comfort, and it reviews the energy supply options for supporting that.

It sets the scene by pointing out that ‘If space heating could be decoupled from water heating it would change the selection criteria for heating appliances and boilers. There would no longer be a need for the heating system (as opposed to the hot water system) to be on standby during summer months or to be capable of operating at a sufficiently high temperature to prevent Legionella developing in water systems. All domestic heating is currently thought of as low-grade heat requirement, but there is a case for distinguishing space heating as low grade and hot water as medium grade. A policy for heat should separate these two different uses’.

It looks at heat pumps as a possibility, but is not too convinced. ‘While the general reduction in carbon intensity of grid electricity makes the use of electric heating (direct or via a heat pump) more attractive, peak heat loads tend to coincide with peak electricity loads. There is, therefore, a significant likelihood of heating demand being met by high carbon electricity generation brought onto the system to meet peak loads over and above the capacity of low carbon generators’.

It goes on ‘Air source heat pumps have been rising in popularity for new build in the UK, but this is partly an effect of the way in which electrical energy is treated in the regulations that makes CO2 targets more lenient than for gas systems.’ While it admits that ‘Air source heat pumps integrate well with well insulated dwellings, if properly sized and installed,’ and it suggests that ‘micro-CHP complements and could balance some of the properties of heat pumps’, it also notes that ‘several reports discuss inadequacies of the application or system engineering in heat pump installations. It is clear that heat pumps are not forgiving if installed inappropriately.’

By contrast, it’s much happier will larger-scale communal system. ‘Communal air source heat pumps are an interesting area of development with some new configurations of systems coming to market. Central systems may be more efficient and are likely to offer much greater energy storage than do systems designed for individual household’.

It adds ‘Larger district systems, incorporating a CHP facility and providing heating are significantly more efficient than domestic level installations. This is because waste heat can be used in district heating after it has generated an element of electricity. Such district heat is therefore always of significantly lower CO2 emissions than any heat only production utilising the same fuel’. And that, it seems, includes domestic scale heat pumps.

The RAE does seem to been moving towards community- scaled system across the board. However, it is less happy with renewables. Although it sees some potential for bioenergy e.g for CHP/District Heating , it is not very impressed with solar, and overall treats renewables as problematic in terms of grid power supply, reverting to the traditional RAE line on the problems of intermittency and the delights of nuclear: ‘During the summer months, most of the night-time load could be provided by nuclear power with renewables providing additional power during the day’, while in winter ‘we would need sufficient renewables to guarantee 40GW during the evening peak. As wind, tides and the sun are intermittent, that would require significantly higher installed capacity of renewables or thermal back-up capacity, much of which would be unused for long periods in the summer’ making renewables uneconomic.

Nevertheless, it does look at smart grid /load management options which might change the situation radically, helping to deal with intermittency. A bit grudging, but at least there is now some recognition that a new interactive supply and demand system might be viable. It’s taken decades to get the community CHP/DH message across to the traditionalist engineers, so maybe it’s too early for idea of smart dynamic grids to have got through! And it may take even longer for them to give up on ‘baseload’ nuclear, which they still see as essential, rather than as getting in the way of a more interactive flexible system based on renewables ( which is the view emerging from Germany) .

However, as far as CHP/DH in concerned, the RAE is now full of praise. It says that ‘CHP plants, biomass combustion, and heat pumps are more efficient, reliable and cheaper at scales larger than a single dwelling. The costs of large scale heat pump installations per kW are a quarter of that for domestic-scale installations.’ It adds that ‘it is more efficient to use the available skills for fewer large systems than for many individual units’, and that, since energy storage will be needed ‘district heating systems have another important benefit – the mass of water in the underground pipes provides a heat store that evens out daily peaks and troughs in demand. This can be supplemented by hot water tanks to increase energy storage’. And taking it one step further, it points out that ‘well insulated hot water tanks or underground inter-seasonal thermal stores will be simpler to provide on a community basis given the small (and reducing) size of most UK homes’.

Some sense last! And DECC seem to be taking notice, in their new Heat strategy- see my next Blog.

‘Heat: degrees of comfort?’ Royal Academy of Engineering www.raeng.org.uk/heat

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